Hello all. I'm installing a backsplash for a friend of mine this weekend and need some advice. I've tiled a few bathrooms and floors over the years but always used cbu. This is the first time I'll be using bare sheetrock. Half of the joints are already taped with joint compound; the other half I'll tape and mud with thinset. Now, how should the joint compound be prepped? I imagine it needs to be sealed with some sort of primer. Also, should I wipe the sheetrock with a damp sponge before applying thinset to lessen the effect of pulling moisture from thinset? Thanks